| Senescence is a degenerate process of tissues and organs in function and morphology in a span life, and the senescence of central nervous system has a dominant status in aging. Changes of pathology were discovered mostly in cerebral cortex and hippocampus. The number of cells will decrease quickly when human reaches old years,and a larger amount of lipofuscin are discoved in cells. So it is very important to study the senescence of cerebrum and hippocampus in order to learn the process and mechanism of senescence.The free radical theory of aging indicated that cellular degeneration was resulted from the excessive free radical that produced in the process of normal cellular metabolism as growth. The main reason of enescence with D-galactose is oxides and peroxides of the excessive superoxidative anion produced in the metabolism.In our study, methods of morphology observations and function mearments were used in order to reveal the effects of swimming training on hippocampus of the central nervous system of the SD rats. The 2-month-old male rats were divided into five groups at random, ten in each group. Normal control group(group C) was given saline(1ml/kg) every day, D-Galgroup(group D) was given D-galactose(50mg/kg) every day, D-Gal and no loading swimming group(group DS1) was given D-galactose(50mg/kg) and swimming with no loading everyday。D-Gal and 3% loading swimming once group(group DS2) was given D-galactose (50mg/kg) and swimming with 3% of body weight attached to theire tails once very day。D-Gal and 3% loading swimming twice group(group DS3) was given D-galactose (50mg/kg) and swimming with with 3% of body weight attached to theire tails twice very day。D-galactose were given for 10 weeks.After eight weeks, learning and memory ability, staying balance and power ability were meared。After 10 weeks, we collected hippocampus, then the contents of MDA and the activities of SOD and GSH-Px in hippocamps were measured with biochemistry methods.Ultrastructures of tissues were observed with electron microscope. The results showed that(1)Under electron microscope, large amounts of neurons in normal control group,extensive putrescenced hippocampus cells condensed, vacuolated neurons in D-Gal group, and most hippocampus cells were not changed and only small neurons slightly vacuolated in DS were observed respectively.(2)Learning and memory ability: In Y-maze, compared with group C and D, the error times for learning and memory of group DS decreased significantly (P<0.01). but compared with D ,there are none of obvious difference ;Staying balance and power ability: Compared with group D, the sling time of group C and DS increased significantly (P<0.01); group DS showed a significantly increase in learning and memory and Staying balance and power ability as compared with group C and D after 8-week swimming training (P<0.05).(3)MDA contents of group C decreased more significantly than that in D-Gal group, and the activity of SOD and GSH-Px increased more significantly than that in D-Gal group. MDA contents of swimming training group decreased more significantly than that in D-Gal group, the activity of SOD increased than that in D-Gal group ,the activity of GSH-Px increased more significantly than that in D-Gal group.It can be concluded that the aging model of rat with D-galactose could be built in some time; swimming training could promote activity of superoxide dismute and glutathione peroxidase, reduce the content of lipid peroxide and prevent the damages of free radical and its production to biological membrane and big biological molecules.So that they could make neurons stay at normal functions, and delay the procession of senescence of central nervous system.
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